as someone who doesn't drive and isn't well-versed in what all the signage means exactly:

the traffic rules are an awful UX experience. highly confusing and often not intuitive at all.

you just have to memorise the rules. if we could start over with traffic rules, you'd just need to read a pamphlet to figure them out.

there isn't really a simple/elegant overarching principle to the traffic system. it's just a bunch of specific rules that accumulated over time, and now we're stuck with them.